But perhaps none of the battles is more striking than the one in Hancock County, about 100 miles southeast of Atlanta, where three in four of the roughly 10,000 residents are black. The racial divide here is deep and prolonged; the white mayor of the county seat, Sparta, made headlines in 1970 after responding to black citizens’ school-desegregation protests by equipping the town’s six-member police force with submachine guns.

...The board first proposed to close all but one of the county’s 10 polling places, a move the N.A.A.C.P. and other minority advocates argued would disenfranchise rural blacks who could not travel long distances to vote. Board members eventually chose to eliminate just one predominantly black precinct. But around the same time, they began to winnow the county’s roll of registered voters, ordering an aide to compare the registrants’ stated addresses with those on their driver’s licenses to spot voters who had moved after registering to vote.